/Engine/Plugins/Developer/Concert/ConcertMain/Source/ConcertTransport/Public/ConcertTransportMessages.h
Acknowledgment messages to reliable events
[USTRUCT](Programming/UnrealArchitecture/Reference/Structs)() struct FConcertAckData : public [FConcertMessageData](API\Plugins\ConcertTransport\FConcertMessageData)
int64
AckSendTimeTicks
Time when this acknowledgment was sent (UTC)
FGuid
SourceMessageId
ID of the source message we're acknowledging